Fibrous product and method of manufacturing same



Aug. 19, 1969 A. MEYER ETAL 3,461,662

FIBROUS PRODUCT AND METHOD OF MANUFACTURING SAME Filed Oct. 2, 196? FIG.|

FIG.2

August K. Meyer Robert B. McFull INVENTORS ATTORNEYS United States Patent US. Cl. 57-154 8 Claims ABSTRACT OF THE DISCLOSURE An improved fibrous product comprising, for example, a polyolefin sheet having talc dispersed therein in an amount between about 4% to about 15% by weight and fractured into substantially interconnected strands, twisted into a twine, cordage, or yarn-like form. v

A method for manufacturing an improved cordage product comprising, for example, the steps of (a) forming a polyolefin sheet having talc dispersed therein in anamount between about 4% and about 15% by weight, (b) fracturing the sheet into a web of substantially interconnected strands, and (c) twisting the fractured sheet into fibrous product form.

This invention relates to an improved thermoplastic fibrous product and, in addition, relates to a method for manufacturing the improved thermoplastic fibrous product wherein the resistance to abrasion and raveling ends of the product is substantially increased.

Fibrous products are well known and include such items as cord, twine, rope, string, yarn and the like, all of which find a multiplicity of uses in industry as, well as in the home. Of course, the most obvious use for such products is in the tying and binding of packages, cartons, as rug backing, or carpet face yarnsand the like. Such a use, whether it is an industrial or a home use, creates an environment where the product is subjected to quite a bit of abrasive Wear. In addition, problems arise with the unraveling of cut ends of the fibrous product after it has been cut to the desired length.

Historically, fibrous products such as those listed above a have been manufactured from natural fibers as jute, hemp, sisal, cotton and the like. However,.natural fiber materials have been found to possess a number of disadvantages which make their use, in certain circumstances, 1

undesirable in fibrousend products. For example, natural fibers'are susceptible to attack by mold bacteria as well as by various insects which cause decay or rotting of the fibers. This disadvantage alone causes natural fiber to lose its strength, as well as usefulness, in many applications. 1

To circumvent the natural fiber decay problem, it has been proposed to manufacture fibrous products from thermoplastic materials because it. is well known. that products have been substantially solved by the product and method for manufacturing same disclosed in US. 3,214,899. This patent discloses a cordage type product formed from a thermoplastic sheet, the sheet having been fractured into a network of interconnected strands. After the thermoplastic sheet is transformed into the web or network of interconnected strands, the strands are twisted together to provide a fibrous product. The invention of US. 3,214,899 has proved an important advance over the prior art in that the product there described has a relatively softer hand, increased strength stability, and increased knot retention stability over previously known products.

For some applications, however, the cordage product that is disclosed in US. 3,214,899 has characteristics that can be improved so as to make it even more useful. One of these characteristics is that the cordage product of U.S. 3,214,899 tends to unravel somewhat at its ends upon being'cut making it difficult to thread through, for example, tying machines and also detracts from its appearance. Another characteristic is that if a satisfactory hand is maintained the abrasion resistance of the fibrous product has been found insuflicient for some purposes.

The above enumerated characteristics of prior art fibrous product are improved in accordance with this invention by forming the product from a polyolefin sheet having talc dispersed therein in an amount between about 4% and about 15% by weight of the polyolefin fractured into a web or network of substantially interconnected strands and twisted into final product form. The method for manufacturing the improved cordage product of this invention comprises the steps of (1) forming a polyolefin sheet having talc dispersed therein in an amount between about 4% and about 15 by weight, (2) fracturing the sheet into a web of substantially interconnected strands, and (3) twisting the fractured sheet into final product form.

It has been unexpectedly found that by adding talc to the polyolefin sheet, the abrasion resistance and unraveling resistance of the end product is substantially increased without loss of softness of hand. Thus, the improvement in accordance with this invention is, basically stated, the addition of talc to the polyolefin sheet from which the fibrous product is made.

The primary objective of this invention has been to provide a polyolefin cordage product having both a pleasing hand and increased abrasion resistance and increased resistance against unraveling of cutends over the ,cordage product described in US. 3,214,899.

Other objectives. and advantagesof this invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

thermoplastics possess a high degree of resistance to degradation by mold, bacteria and insects. Nevertheless, difficulties have been found to exist infibrous products manufactured with thermoplastics. For example, the thermoplastic cordage products have been found to be relatively slippery, thereby providingarelatively low degree become undone. Also, the thermoplastic fibrous products of the past have not had a soft hand and, therefore, have been relatively diflicult to usein packaging-apparatus and unsuitable for use as a yarn-like product. a a

Such problems in the prior art of synthetic fibrous FIGURE 1 is a diagrammatic view of a. typical equipment line for producing cordage products in accordance with the principles of this invention, and

FIGURE 2 is a diagrammatic illustration of an abrader used to test the abrasion resistance of cordage products manufactured according to this invention. a

A typical equipment line for producing cordage products, in accordance with this invention, is illustrated in FIGURE 1 and includes an extruder 10 having a hopper 12 and an extruder die 14. A quenching bath 16 and a heated oven 18 are located downstream. from the extruder 10. A set of pull out rolls 20 are located in the quench bath 16' and a set of S-wrap rolls 22 are positioned at the inlet end 24, of the oven 18 and a set of S-wrap rolls 26 are positioned at the outlet end 28 of the oven. Rolls 30 and 32 guide the extruded film or sheet 34 from the quenching bath 16 to the S-wrap rolls 22. Downstream from the S- wrap rolls 26 is located a high pressure air-jet beater 36. A collection hopper or container 38 located at the outlet 3 side of the jet beater 36 receives the fractured film 40. A conventional type twister-winder 42 is disposed at the end of the illustrated equipment line and receives fractured film 40 from a collection hopper 38.

In operation, the extruder is fed with a polyolefin provided with a suitable amount of talc through the hopper 12, and the extruder forms a sheet or film 34 that exits from the extruder die 14. The sheet or film 34 is drawn away from the die 14 by means of pull out rolls 20 located in quench bath -16 which serves to solidify the film. The film is then threaded to the S-wrap rolls 22 and is longitudinally. drafted or drawn by rotating the S-wrap rolls 26 at a higher peripheral speed than the rolls 22. Simultaneously with the drafting of the sheet 34, it is heated by passing it through the oven 18. This treating of the film sheet 34, that is, the combined heating and longitudinal drafting, causes it to become substantially unilaterally oriented and enhances the strength characteristics of the sheet in the machine direction and produces in the sheet a large number of lines of potential or incipient cleavage parallel to the edges thereof.

The sheet 34 is then subjected to one or more air jet beaters 36 where it is fractured into a web or fracture film 40 of interconnected strands as disclosed in the aforesaid U.S. Patent No. 3,214,899. Thereafter the fractured sheet or web 24 is deposited into a collecting container 38. Subsequently the fractured web or film 40 is withdrawn from a collection container 38 which imparts to the web 42 the desired degree of twist, thereby forming a polyolefin fibrous product.

The method for manufacturing an improved fibrous product, according to this invention, basically includes the steps of (1) creating a polyolefin sheet having talc dispersed therein in an amount between about 4% and about by weight, (2) fracturing or splitting the sheet into a web of substantially interconnected strands, and (3) manipulating the fractured sheet into final product form.

The polyolefin sheet having talc dispersed therein is created by first associating the talc with the polyolefin feed material prior to extrusion of the feed into sheet form. Such association or combination of the talc with the polyolefin is preferably carried out so that the talc is substantially homogeneously distributed throughout the polyolefin. A homogeneous dispersion of the talc within the polyolefin is necessary so as to achieve a homogeneous distribution of the tale within the sheet. The polyolefin, with the talc, is then extruded into sheet form, the sheet having the talc intimately associated therewith and homogeneously distributed throughout.

Preferably, the talc is combined with the polyolefin in an amount between about 4% to about 15 by weight of the polyolefin material. It has been found that talc concentrations in the polyolefin feed greater than about 15% have adverse effects on the physical properties of the fibrous product, for example, tensile properties, as such properties start to decrease at talc concentrations above this level. Talc concentrations less than about 4% do not provide the desired benefits of abrasion resistance and cut end unraveling resistance.

The talc may be incorporated with the polyolefin prior to extrusion of the polyolefin sheet by any of numerous known techniques. For example, the talc can be intimately and homogeneously distributed with the polyolefin by means such as Banbury mixing, rolling, re-extruding, or surface coating. Substantially any of these methods may be used to achieve an intimate mixture between talc and thermoplastic material; however, in general, the mixing method selected will be somewhat dependent upon the particle size of the talc. The only limitation on the mixing method employed is that the tale must be substantially homogeneously mixed with the polyolefin, that is, sporadic high concentrations of the talc within the polyolefin are not desired.

Preferably, a polyolefin concentrate containing from about 25% to about 50% talc is preliminarily prepared by one of the above noted mixing methods. This pre- 4 liminary talc-polyolefin concentrate is then added to or intermixed with a talc free polyolefin prior to extruding the sheet. That is, the talc free polyolefin and the talcpolyolefin concentrate are introduced into the extruder in predetermined amounts, so as to give the desired level of talc in the extrudate or sheet being formed. The concentrate may be added by any known means for metering additives to a feed stream such as, for example, screw type feeders or a rotating valve.

Preferably, the extruded polyolefin sheet is then treated, prior to fracturing, to enhance its strength characteristics. Such treating includes the steps of simultaneously drafting and heating the sheet to provide unilateral orientation. It is preferred that the polyolefin sheet be drawn within a drafting ratio of about 3:1 to about 15:1 while being subjected to a temperature of between about 300 F. to about 350 F. This treatment creates a large number of cleavage lines.

Subsequently, the oriented polyolefin sheet is fractured to transform the continuous sheet into a web-like form having interconnected strands. The fracturing step may be carried out by any well known fracturing or splitting means or apparatus such as, for example, air jet beaters, rotary brushes, and other types of mechanical beaters. It is preferred to use an air jet beater or series of air jet beaters as the degree of fracturing can be controlled to give the desired end product physical characteristics. In this method, the air pressure applied to the air jet beaters bears a direct relationship to the thickness of the sheet to be fractured. For example, air jet beater pressures of 5- p.s.i. are useful for polyolefin sheets having thicknesses of between about .001 inch and about .005 inch.

Normally, fibrous products to be used as rope, twine, and the like, will only be fractured to a relatively limited extent so as to provide a reasonable amount of residual inherent fracturability. The residual inherent fracturability permits additional fracturing with the web or sheet when knots are tied to provide good knot stability.

As a general rule, the lower the residual inherent fracturability of the polyolefin cordage, the more interconnected strands will be present and the fibrous product more closely resembles a web than a sheet. Alternatively, the higher the residual inherent fracturability of the cordage, up to a practical limit, the less interconnected strands will be present and the fibrous product more closely resembles a sheet. By residual inherent fracturability we mean the ability of a thermoplastic sheet to be additionally fractured, after the initial fracturing step has been performed, into additional strands and/or fibrils that are interconnected in web-like form.

' The fractured sheet or web, now in the form of numerous substantially interconnected strands, is twisted or manipulated into a final form preferably by means of a conventional twister. The twister permits the impartation and regulation of a desired degree of twist as the web is twisted into the final product form.

Thus, the improved fibrous product manufactured in accordance with the above method comprises a partially split or fractured polyolefin sheet of substantially interconnected strands, the sheet having been twisted into cordage form, and talc dispersed within the sheet in an amount between about 4% and about 15% by weight of the polyolefin. Such a polyolefin fibrous product has improved abrasion resistance and cut-end unraveling resistance over those values exhibited by the product of U.S. 3,214,899 without loss of the pleasing hand of the product of this patent.

It has been found that the addition of talc does not substantially affect the physical properties of the polyolefin cordage as compared to those properties possessed by polyolefin cordage made without talc when used in the quantities and manner specified herein. In addition, the presence of talc in the polyolefin cordage product does not adversely affect the stability, that is, the weathering resistance, ultraviolet light resistance, and heat resistance, of the polyolefin cordage.

The abrasion resistance of the cordage product manufactured in accordance with this invention is measured in an abrader that is illustrated in FIGURE 2. The abrader comprises a hollow drum 41 that is rotatable about an abrasion block 42. The abrasion block 42 is mounted on a stationary arm 43. A compression spring 44 is biased against the abrasion block 42 so as to produce an abrasion pressure of about 20 p.s.i. between the block and each of a plurality of sample mounting plates 45, the mounting plates 45 being mounted about the periphery of the hollow drum 41. Each sample mounting plate 45 is provided with a knob 46 that projects inwardly toward the drum center and is positioned in such a manner so as to engage the abrasion blocks working surface 47 as the drum 41 rotates about the abrasion block apparatus, thereby creating the abrasion pressure. The sample plates 45 are removably mounted on the drum periphery and are held thereto by means of thumb screws 48 that cooperate with T-mounts 49 integral with the drum surface.

In operation, the sample mounting plates 45 are removed from engagement with the periphery of the drum 41, and each is provided with a cordage sample across the knob 46. Thereafter, the mounting plate-cordage sample combination is reinserted into operative engagement with the drum 41. The drum 41 is then rotated, the abrasion block 42 remaining fixed, so that the cordage sample on each knob contacts the abrasion block 47. For purposes of this invention, one complete cycle is considered to be 360 revolution of the hollow drum 41. In the apparatus shown, twelve different cordage samples can be tested at the same time because of the twelve knobs 46 or, alternatively, twelve cordage samples from a single twine length may be tested to obtain a statistical survey of that twines abrasion resistance.

This invention is further illustrated by the following examples; however, it is not intended to limit the scope of the invention by the examples but merely to illustrate it. All percentages are expressed as percent by weight of the polyolefin feed unless otherwise stated.

Example I A polypropylene concentrate containing 50% talc is prepared by Banbury mixing. This concentrate is blended with polypropylene in an amount sufficient to give talc in the final polyolefin blend.

The polypropylene blend is extruded at a melt temperature of 280 C. through a die having a die lip opening of 11 x .02" at a rate of 44 pounds per hour into a sheet. The extruded sheet is immediately quenched in chilled water.

The sheet is then oriented by drafting it at a draw ratio of 12:1 through a forced air oven heated to 165 C., the output line speed being 520 ft./min. The final film thickness is 2.8 mils. The oriented film is then fractured by an air jet and twisted into a twine. The fibrous product so prepared has the following properties:

Tenacity, gm./ den 3.7 Elongation, percent 9.0 Knot strength, gm./den. 2.4 Knot elongation, percent 12.0

The fibrous product is checked for abrasion resistance after 300 cycles in the abrader described above. Whereas a fibrous product formed from a sheet containing no tale is substantially abraded away after 300 cycles, the product of this example is only slightly damaged by the action of the abrading surface.

The fibrous product is evaluated for end unraveling characteristics by rapping the end of freshly cut product on a desk top and checking the degree of flare that occurs. The product of this example did not have a tendency to unravel when submitted to this test as contrasted to a product containing no tale in which a distinct tendency to unravel and to flare was noted when the same test was applied.

6 Example 11 A polypropylene concentrate containing 50% tale is prepared by Banbury mixing. This concentrate is blended with a polypropylene in an amount su'fficient to give 5% talc in the final polyolefin blend.

The polypropylene blend is extruded at a melt temperature of 280 C. through a die having a die lip opening of 11" x .02" at a rate of 46 pounds per hour into a sheet. The extruded sheet is immediately quenched in chilled water.

The sheet is then oriented by drafting in at a ratio of 12:1 through a forced air oven heated to 170 C., the output line speed being 520 ft./min. Final film thickness is 3.0 mils.

The oriented sheet is subsequently partially fractured by an air jet operating at a pressure of 12 p.s.i. Subsequently, the interconnected strand web is twisted into a fibrous product having a denier of 17,100. The product so prepared has the following physical properties.

Tenacity, gm./den. 3.3 Elongation, percent 7.7 Knot strength, grn./den. 2.5

Knot elongation, percent 12.0

The abrasion resistance of this twine, measured by the abrader, is substantially better than a similar polypropylene twine made without talc, but is not quite as good as the abrasion resistance of the twine in Example I.

The twine of this example has a substantially less tendency to unravel when cut than a similar polypropylene twine without talc.

Example III A polypropylene concentrate containing 50% tale is blended with polypropylene in an amount sufiicient to give 15% tale in the final polyolefin blend. The polypropylene blend is then extruded at a melt temperature of 280 C. through a die having a die lip opening of 11" x .02". The resultant polypropylene sheet is quenched in chilled water.

Thereafter, the resultant sheet is drafted at a ratio of 12:1 in a forced air oven having air heated to C., the output line speed being 510 ft./min. The final film thickness is 2.9 mils.

The oriented sheet is then partially fractured by an air jet operating at a pressure of 15 psi. The resultant interconnected strand sheet or web is then twisted at a rate of 0.8 twist per inch to give twine of 17,800 denier. The physical properties of the twine of this example are as follows:

Tenacity, gm./den. 2.8 Elongation, percent 7.8 Knot strength, gm./den. 2.2

Knot elongation, percent 11.2

The abrasion resistance and resistance toward unraveling of the twine ends is far superior to those characteristics of a similar fibrous product made without the tale.

While the resultant product has been described throughout this description as one which is twisted, it is apparent that the fibrous product according to this invention can be utilized in the untwisted state. For example, the fibrous product can be formed into a non-woven batting or fabric in the untwisted state. Regardless of the manner of usage, the addition of talc results in a product having the desired improved characteristics described herein.

Although the invention has been described in considerable detail with particular reference to certain preferred embodiments thereof, variations and modifications can be effected within the spirit and scope of the invention as described hereinbefore.

What we desire to claim and protect by Letters Patent 1s:

1. An improved fibrous product comprising:

(a) a web of flat, filamentary-like strands discontinuously and randomly separated from each other yet interconnected with said web;

8 (b) said web being characterized in that the material 5. A method as set forth in claim 4 wherein said com of said web is an extrudable, polyolefin containing bining step comprises the steps of: between about 4% to about 15% by weight of talc (a) preliminarily preparing a polyolefin concentrate uniformly dispersed therein to thereby increase the comprising between about 25% and about 50% by abrasion resistance and lessen the tendency of said 5 weight talc, and fibrous product to flare open from the twisted form (b) thereafter intermixing said polyolefin concentrate while maintaining adesirable hand. with additional polyolefin feed material, said con- 2. A product according to claim 1 wherein said web stituents to be intermixed in a manner that provides is twisted into final product form. a final talc concentration within said polyolefin sheet 3. A product according to claim 2 wherein said polybetween about 4% and about by weight. olefin is polypropylene. 6. A method as set forth in claim 4 wherein said poly- 4. A method for manufacturing an improved fibrous olefin sheet is of a drawn thickness of less than about 4 product comprising the steps of: mils.

(a) homogeneously mixing a organic plastic material 7. A method as set forth in claim 4 wherein said fibrilconcentration with talc; 15 lating step is accomplished by subjecting said polyolefin (b) forming said mixture into a sheet containing besheet to an air flow directed on it by air jet heaters.

tween about 4% to about 15% by weight of said 8. A method as set forth in claim 4 wherein said web talc; is twisted into final product form. (0) drawing said sheet at a drafting ratio of from about 3:1 to about 15:1 while subjecting it to an elevated References Cited temperature of from about 300 F. to about 350 F. UNITED STATES PATENTS thereby achieving a relatively high degree of molecular orientation and increasing the strength of said 2920349 H1960 White sheet longitudinally but not transversely thereof and g qfi et 3 producing in said sheet a large number of lines of po- 33 1 8/1967 D 1 T 1 tential or incipient cleavage; Y a

3,382,663 5/1968 Frielmgsdorf 57167 XR (cl) fracturing said sheet by subjecting it to forces which tend to convert at least some of said lIHGS Of potent al JORDAN FRANKLIN, Primary Examiner cleavage to randomly spaced, discontinuous slits through said film thereby forming a web of flat, fila- WERNER SCHROEDER, Assistant EXaIniIwf mentary-like strands, discontinuously and randomly separated from each other yet interconnected with said web. 57-140, 157, 165, 167; 260-37; 264-210 

